Fixed point structure of the Abelian Higgs model

Understand

The order of the superconducting phase transition is analyzed via the functional renormalization group approach.

• For the first time, we derive fully analytic expressions for the $\beta$ functions of the charge and the self-coupling in the Abelian Higgs model with one complex scalar field in $d=3$ dimensions that support the existence of two charged fixed points: an infrared (IR) stable fixed point describing a second-order phase transition and a tritical fixed point controlling the region of the parameter space that is attracted by the former one.
• It is found that the region separating first- and second-order transitions can be uniquely characterized by the Ginzburg-Landau parameter $\kappa$, and the system undergoes a second order transition, only if $\kappa>\kappa_c \approx 0.62/\sqrt2$.